a. Field of the Invention
The instant invention generally relates to medical devices incorporating one or more bimaterial valves to provide fluid control and methods for using the devices for treatments that benefit from device fluid perfusion or device cooling fluids. In particularly preferred embodiments, the instant invention relates to devices and methods for treating electrophysiological diseases of the heart, such as epicardial ablation for the treatment of atrial fibrillation. More generally, the present invention relates to devices and methods for the improved delivery of a flowable material to a target tissue.
b. Background Art
In performing a number of minimally invasive procedures, such as cardiac ablation of an epicardial tissue, it is desirable to maintain or control the tissue at an appropriate temperature to avoid undesirable thermal damage. A flowable material, such as saline, may be used to cool or temperature-control tissue and to maintain adequate acoustic contact between an acoustic ablation device and a tissue. The source of flowable material can be an intravenous bag of saline in which the flow is gravity driven or a positive displacement pump. For medical devices having multiple internal points of flow control, for example ablation devices having multiple ablation cells or elements, fluid may flow to each ablation cell at approximately the same rate in both an unpowered “standby” mode and in a powered ablating mode. However, in practice, the ablation cells may be activated in phases such that some cells are active while others are inactive. Enough coolant must be provided to all cells simultaneously as if all are operating. Further, if some cells tend to operate hotter than others, there is no mechanism for maintaining a peak temperature across all cells other than decreasing the power to the hotter cells. It would be desirable to be able to selectively deliver a larger amount of coolant to an individual cell so that each cell could more efficiently deliver the needed ablation and still remain below a peak design temperature.
A disadvantage of the existing devices and procedures is that the flow rate of a fluid to the individual cells is not individually controlled or adjustable. It is therefore desirable to provide devices and methods having individual flow rate control at the level of each cell based on temperature changes to allow for higher flow rates to active cells and lower flow rates to inactive cells.